Liquid transport device and liquid transport method

ABSTRACT

A liquid transport device includes an elastic tube, fingers that line up along a transport direction, a drive mechanism that drives the fingers, a temperature sensor that measures the ambient temperature of the tube, and a control unit. The control unit controls the drive mechanism such that the finger on the most upstream side of the transport direction starts a closing operation of squeezing the tube after the finger on the most downstream side of the transport direction completes the closing operation of squeezing the tube, and the finger second from the downstream side completes an opening operation of being pressed back by the tube. The control unit controls the rate of driving of the drive mechanism in a corrective manner based on a result of measurement by the temperature sensor. The liquid transport device can transport a liquid with high accuracy regardless of the ambient temperature of the tube.

BACKGROUND

1. Technical Field

The present invention relates to a liquid transport device and a liquidtransport method.

2. Related Art

As a liquid transport device, there is known a device in which aplurality of fingers arranged along an elastic tube is pressed by a camand sequentially squeezes the tube to transport a liquid in the tube.Such a liquid transport device is used for injecting a liquid medicinesuch as insulin into a body. However, depending on the ambienttemperature at which the liquid transport device is used, the rigidityof the tube differs, and the rate of flow of the liquid flowing throughthe tube is not constant. Thus, there is proposed a method that controlsthe speed of rotation of a motor on the basis of a temperature that isdetected by a temperature sensor disposed in the vicinity of the tube.

As described above, in the device that transports a liquid with thefingers squeezing the tube, the amount of transport of a liquid isdetermined by the amount of a liquid that is captured in the tube whenthe fingers on the upstream side of the tube squeezes the tube.Therefore, simply changing the speed of rotation of the motor dependingon the temperature in the vicinity of the tube, as disclosed inJP-A-10-216226, causes the state of restoration of the tube that issqueezed by the finger on the downstream side to vary when the finger onthe upstream side squeezes the tube, and variations occur in the amountof a liquid that is captured in the tube, that is, the amount of aliquid to transport. Thus, it is not possible to transport a liquid withhigh accuracy.

SUMMARY

An advantage of some aspects of the invention is to provide a liquidtransport device and a liquid transport method that transports a liquidwith high accuracy regardless of the ambient temperature of a tube.

An aspect of the invention is directed to a liquid transport deviceincluding a tube that has elasticity and is intended to transport aliquid in a transport direction, a plurality of fingers that is lined upalong the transport direction, a drive mechanism that drives theplurality of fingers, a temperature sensor that measures the ambienttemperature of the tube, and a control unit that controls the drivemechanism in a manner in which a liquid inside the tube is transportedin the transport direction by repeating a closing operation of squeezingthe tube with the finger and an opening operation in which the finger ispressed back by the shape of the squeezed tube being restored, in whichthe control unit controls the drive mechanism in a manner in which thefinger on the most upstream side of the transport direction starts theclosing operation after the finger on the most downstream side of thetransport direction completes the closing operation, and the finger thatis second from the downstream side of the transport direction completesthe opening operation, and controls the rate of driving of the drivemechanism in a corrective manner on the basis of a result of measurementby the temperature sensor.

Other features of the invention will become more apparent from thedisclosure in the present specification and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is an exploded view of a liquid transport device.

FIG. 2 is a transparent top view of the inside of the liquid transportdevice.

FIG. 3 is a cross-sectional view of the liquid transport device.

FIG. 4A is a diagram describing the inside of a finger base, and FIG. 4Bis a block diagram describing a control unit of the liquid transportdevice.

FIG. 5 is a diagram describing control of operation of a finger in anembodiment.

FIG. 6 is a diagram describing control of operation of the finger in theembodiment.

FIG. 7 is a diagram describing control of operation of a finger in acomparative example.

FIG. 8 is a diagram describing control of operation of the finger in thecomparative example.

FIG. 9 is a graph illustrating the amount of transport of a liquid whenthe ambient temperature of a tube and the speed of rotation of a cam arechanged.

FIG. 10 is a diagram representing a difference in the cross-sectionalextent of the tube due to a difference in the ambient temperature of thetube.

FIG. 11 is a correction table for the amount of rotation of the cam.

FIG. 12 is a flowchart of the flow of a liquid transport method in theliquid transport device.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

At least the following items are apparent from the disclosure in thepresent specification and the appended drawings.

A liquid transport device includes a tube that has elasticity and isintended to transport a liquid in a transport direction, a plurality offingers that is lined up along the transport direction, a drivemechanism that drives the plurality of fingers, a temperature sensorthat measures the ambient temperature of the tube, and a control unitthat controls the drive mechanism in a manner in which a liquid insidethe tube is transported in the transport direction by repeating aclosing operation of squeezing the tube with the finger and an openingoperation in which the finger is pressed back by the shape of thesqueezed tube being restored, in which the control unit controls thedrive mechanism in a manner in which the finger on the most upstreamside of the transport direction starts the closing operation after thefinger on the most downstream side of the transport direction completesthe closing operation, and the finger that is second from the downstreamside of the transport direction completes the opening operation, andcontrols the rate of driving of the drive mechanism in a correctivemanner on the basis of a result of measurement by the temperaturesensor.

According to the liquid transport device, a liquid can be transportedwith high accuracy regardless of the ambient temperature of the tube.

In the liquid transport device, it is preferable that the rate ofdriving of the drive mechanism is the amount of rotation of the drivemechanism.

According to the liquid transport device with this configuration, sincethe amount of rotation of the drive mechanism is corrected, errorshardly occur in the amount of rotation of the drive mechanism whencompared with a case of correcting the speed of rotation of the drivemechanism (amount of rotation per unit time), and a liquid can betransported with high accuracy.

In the liquid transport device, it is preferable that the drivemechanism includes a piezoelectric motor, and the temperature sensor isa sensor that measures the ambient temperature of the piezoelectricmotor for use in control of drive of the piezoelectric motor.

According to the liquid transport device with this configuration, thenumber of components can be reduced when compared with a case where adedicated sensor that measures the ambient temperature of the tube isdisposed separately from a sensor that measures the ambient temperatureof the piezoelectric motor, and cost can be reduced.

In the liquid transport device, it is preferable that the control unitcontrols the drive mechanism in a manner in which the speed of drive ofthe drive mechanism is constant.

According to the liquid transport device with this configuration, aliquid can be transported with high accuracy regardless of the ambienttemperature of the tube, and control by the control unit can befacilitated when compared with a case of changing the speed of drive ofthe drive mechanism depending on the ambient temperature of the tube.

In the liquid transport device, it is preferable that the control unitchanges the speed of the drive mechanism to an extent in which thefinger on the most upstream side starts the closing operation after thefinger on the most downstream side completes the closing operation, andthe finger that is second from the downstream side completes the openingoperation.

According to the liquid transport device with this configuration, aliquid can be transported with high accuracy regardless of the ambienttemperature of the tube, and the processing time of a transportoperation (time of transport of a predetermined amount of a liquid) canbe adjusted by adjusting the speed of drive of the drive mechanismaccording to the corrected rate of driving of the drive mechanism.

In the liquid transport device, it is preferable that the extent of thecross section of the inside of the tube after the opening operation iscompleted, the cross section being taken by cutting the tube in adirection that is perpendicular to the axial direction of the tube,changes depending on the ambient temperature of the tube.

According to the liquid transport device with this configuration, aliquid can be transported with high accuracy regardless of the ambienttemperature of the tube.

In the liquid transport device, it is preferable that the control unitcontrols the drive mechanism in a manner in which a transport operationof transporting a liquid in the tube with drive of the plurality offingers and a stopping operation of not transporting a liquid in thetube with stopping of drive of the plurality of fingers are alternatelyrepeated.

According to the liquid transport device with this configuration, aliquid can be transported with high accuracy regardless of the ambienttemperature of the tube, and an increase or a decrease in the processingtime of the transport operation depending on the corrected rate ofdriving of the drive mechanism does not pose a problem. Thus, the extentof freedom is increased insetting the speed of drive of the drivemechanism.

A liquid transport method for a liquid transport device that includes atube which has elasticity and is intended to transport a liquid in atransport direction, a plurality of fingers which is lined up along thetransport direction, and a drive mechanism which drives the plurality offingers, in which a liquid in the tube is transported in the transportdirection by repeating a closing operation of squeezing the tube withthe finger and an opening operation in which the finger is pressed backby the shape of the squeezed tube being restored, the method includesobtaining the ambient temperature of the tube, and driving the pluralityof fingers with the drive mechanism at a rate of driving that iscorrected on the basis of the ambient temperature and driving theplurality of fingers in a manner in which the finger on the mostupstream side of the transport direction starts the closing operationafter the finger on the most downstream side of the transport directioncompletes the closing operation, and the finger that is second from thedownstream side of the transport direction completes the openingoperation.

According to the liquid transport method, a liquid can be transportedwith high accuracy regardless of the ambient temperature of the tube.

Configuration of Liquid Transport Device

FIG. 1 is an exploded view of a liquid transport device 1. FIG. 2 is atransparent top view of the inside of the liquid transport device 1.FIG. 3 is a cross-sectional view of the liquid transport device 1. FIG.4A is a diagram describing the inside of a finger base 202, and FIG. 4Bis a block diagram describing a control unit 110 of the liquid transportdevice 1. The liquid transport device 1 in the present embodimentincludes a main body 10, a cartridge 20, and a patch 30. The main body10, the cartridge 20, and the patch 30 are separable as illustrated inFIG. 1 but are assembled as a single body when used. The liquidtransport device 1 is suitably used for regularly injecting a liquid(for example, insulin) that is retained in the cartridge 20 into aliving body while the patch 30 adheres to a living body. In FIG. 1, theside of the liquid transport device 1 where the liquid transport device1 adheres to a living body is assumed to be a lower side, and theopposite side is assumed to be an upper side.

Main Body 10

The main body 10 includes a piezoelectric motor 100, a speed reducingtransmission mechanism 103, and a cam 104 as illustrated in FIG. 2. Thepiezoelectric motor 100 includes a plate-shaped member 101 and a pair ofsprings 102. The speed reducing transmission mechanism 103 includes arotor wheel 105, an intermediate wheel 106, and an output shaft 107. Theplate-shaped member 101 is biased toward the rotor wheel 105 by theelasticity of the pair of springs 102, and the tip end portion of theplate-shaped member 101 is in contact with the circumferential surfaceof the rotor wheel 105. In addition, the plate-shaped member 101includes a piezoelectric layer and two electrodes. The shape of theplate-shaped member 101 is changed by a change in a voltage applied tothe two electrodes. The rotor wheel 105 is rotated by, for example, theplate-shaped member 101 repeatedly alternating longitudinal vibrationsthat change the length of the plate-shaped member 101 in the widthdirection thereof and flexural vibrations that change the shape of theplate-shaped member 101 into a substantially S shape.

A pinion that rotates together with the rotor wheel 105 is disposed inthe rotor wheel 105. The pinion engages with a teeth portion of theintermediate wheel 106 and rotates the intermediate wheel 106. A pinionis also disposed in the intermediate wheel 106. The pinion engages witha teeth portion of a toothed wheel that rotates together with the outputshaft 107 and rotates the output shaft 107. The cam 104 is disposed inthe output shaft 107. The cam 104 is rotated by rotation of the outputshaft 107. As such, rotation of the rotor wheel 105 is transmitted tothe cam 104 at a predetermined speed reduction ratio. A motor forrotating the cam 104 is not limited to the piezoelectric motor 100 andmay be any motor having a rotating shaft. A secondary battery 108 isdisposed on the lower surface of the main body 10 and is capable ofsupplying a predetermined amount of electricity to each unit of the mainbody 10.

The main body 10 also includes a control unit 110 and a detector group112 as illustrated in FIG. 2 and FIG. 4B. The control unit 110 is anelectronic substrate that includes a CPU 110 a and a memory 110 b and isintended to control a drive mechanism 111 (the piezoelectric motor 100,the speed reducing transmission mechanism 103, and the cam 104)according to a signal from a program and the detector group 112. Thedrive mechanism 111 drives a plurality of fingers 21 illustrated in FIG.4A. The detector group 112 includes a rotary encoder (not illustrated)that measures the amount of rotation of the rotor wheel 105 and the cam104 (angle of rotation), a temperature sensor 109, and the like. Thetemperature sensor 109, for example, is disposed in the vicinity (on theelectronic substrate, which is the control unit 110, in the presentembodiment) of the piezoelectric motor 100 because vibrationcharacteristics of the piezoelectric motor 100 are affected by theambient temperature. The control unit 110 controls drive (drivefrequency) of the piezoelectric motor 100 on the basis of a result ofmeasurement by the temperature sensor 109, that is, the ambienttemperature of the piezoelectric motor 100.

Cartridge 20

The cartridge 20 includes a retaining portion 201 that retains a liquid,the finger base 202, a connecting needle 203, the finger 21, and a tube22 as illustrated in FIG. 3. The tube 22 is a tube that is elastic andis intended to transport a liquid in a transport direction. The endportion of the tube 22 on the upstream side of the transport directioncommunicates with the retaining portion 201, and the end portion thereofon the downstream side of the transport direction communicates with theconnecting needle 203. In addition, as illustrated in FIG. 4A, the tube22 is arranged along an arc-shaped inner circumferential surface 202A ofthe finger base 202. When the main body 10 is attached to the cartridge20, the cam 104 is positioned in the central portion of the finger base202. In the finger base 202, the plurality of fingers 21 is arranged tobe lined up along the arc-shaped tube 22 (along the transportdirection), one end of the finger 21 is in contact with the cam 104, andthe other end thereof is in contact with the tube 22.

The cam 104 has a plurality (four in FIG. 4A) of protruding portions onthe outer circumference thereof. Thus, when the cam 104 rotates, theprotruding portions of the cam 104 press the fingers 21 in order fromthe upstream side of the transport direction, and the fingers 21 squeezethe tube 22 (closing operation). When the fingers 21 are separated fromthe protruding portions of the cam 104, the shape of the squeezed tube22 is restored because of the elasticity of the tube 22, and the fingers21 are pressed back toward the cam 104 (opening operation). The controlunit 110 controls the drive mechanism 111 in such a manner that theclosing operation and the opening operation are repeated. This moves thetube peristaltically, and a liquid inside the tube 22 is transported tothe patch 30 through the connecting needle 203.

Patch 30

The patch 30 includes a catheter 310, an introducing needle 320, anintroducing needle folder 321, a port base 330, and a patch base 340 asillustrated in FIG. 3. The patch base 340 is a plate-shaped member thatis fixed to the port base 330 and covers the lower surface of thecartridge 20. The patch base 340 adheres to a living body. The catheter310 is a tube that is comparatively soft and is inserted and implantedin a living body in order to inject a liquid into a living body. Theintroducing needle 320 is a metal needle for inserting the catheter 310into a living body and is held by the introducing needle folder 321. Theintroducing needle folder 321 is attached to the port base 330 at thetime of the liquid transport device 1 being mounted on a living body.After the introducing needle 320 is inserted into a living body alongwith the catheter 310, the introducing needle folder 321 is plucked fromthe port base 330 along with the introducing needle 320, and only thecatheter 310 is inserted in a living body. The side portion on thecartridge 20 side of the port base 330 communicates with the connectingneedle 203. A liquid from the connecting needle 203 sequentially passesthrough the port base 330 and the catheter 310 to be injected into aliving body.

Control of Liquid Transport Device Filled-Up Time

FIG. 5 and FIG. 6 are diagrams describing control of operation of thefingers 21 in the present embodiment. FIG. 7 and FIG. 8 are diagramsdescribing control of operation of the fingers 21 in a comparativeexample. FIG. 5 and FIG. 7 are diagrams illustrating a relationshipbetween the operation of the fingers 21 and a time. FIG. 6 and FIG. 8are diagrams illustrating the state of the fingers 21 and the tube 22 ata time e. The tube 22 is depicted as a linear shape in FIG. 6 and FIG. 8for simplification of the drawings. In addition, for descriptivepurposes, the fingers 21 are called a first finger 21 a, a second finger21 b, . . . , and a seventh finger 21 g in order from the upstream sideof the transport direction.

As illustrated in FIG. 5, the first finger 21 a, for example, on themost upstream side of the transport direction starts the closingoperation (squeezes the tube 22) when pressed by the protruding portionsof the cam 104 at a time a and completes the closing operation at a timeb, going into a closing state. Completion of the closing operation meansa state where the fingers 21 completely squeeze the tube 22, and aliquid cannot pass through the tube 22. This state is called a closingstate. After being in the closing state continuously for a predeterminedperiod of time, the first finger 21 a is separated from the protrudingportions of the cam 104 at a time c and is just in contact with the tube22 without pressing the tube 22. Then, the tube 22 presses the firstfinger 21 a back with the elasticity thereof, and the first finger 21 acompletes the opening operation at a time d, going into an openingstate. Completion of the opening operation means a state where the shapeof the squeezed tube 22 is restored to the original shape thereof. Thisstate is called an opening state. After being in the opening statecontinuously for a predetermined period of time, the first finger 21 astarts the closing operation again at the time e.

The second to the seventh fingers 21 b to 21 g also operate in the samemanner as the first finger 21 a in order from the upstream side of thetransport direction while the operation thereof is shifted in time by apredetermined period of time (t seconds in FIG. 5). The first finger 21a on the most upstream side of the transport direction starts theclosing operation t seconds after the seventh finger 21 g on the mostdownstream side starts the closing operation (that is, at the time e).There is disposed a moment (time h) at which the first finger 21 a onthe most upstream side and the seventh finger 21 g on the mostdownstream side are closed at the same time. This can prevent backflowof a liquid.

A period from the start of the closing operation by one finger 21 (forexample, the time a) until the restart of the closing operation by thatfinger 21 (for example, the time e) is called one cycle. The amount of aliquid transported in one cycle is an amount of a liquid that iscaptured in the part of the tube 22 where the first finger 21 a to thesixth finger 21 f abut on at the time e in FIG. 5, that is, at a pointin time when the seventh finger 21 g is in the closing state, and thefirst finger 21 a starts the closing operation. For example, in FIG. 6,a liquid with which the area illustrated by the hatched portion insidethe tube 22 is filled is the amount of a liquid that is transported inone cycle. The amount of liquid corresponding to one cycle istransported toward the downstream side of the transport direction whenthe first finger 21 a is closed, the seventh finger 21 g is opened, andthe second to the sixth fingers 21 b to 21 f are sequentially closedfrom the state of FIG. 6.

The resilience of the tube 22 differs depending on a difference in thematerial and the like that constitute the tube 22. Thus, a differenceoccurs in a period during which the fingers 21 are separated from theprotruding portions of the cam 104, start the opening operation, andcomplete the opening operation, that is, a period during which thesqueezed tube 22 is restored to the original shape thereof (for example,from the time c to the time d). For this reason, when the operation ofthe fingers 21 in a case of using a tube 22 having weak resilience iscontrolled in the same manner as in a case of using a tube 22 havingstrong resilience, the time e at which the first finger 21 a starts theclosing operation is earlier than a time f at which the sixth finger 21f completes the opening operation as illustrated in the comparativeexample in FIG. 7. Then, as illustrated in FIG. 8, the amount of aliquid captured in the part of the tube 22 where the first to the sixthfingers 21 a to 21 f abut on is less than that illustrated in FIG. 6. Assuch, when the first finger 21 a starts the closing operation before thesixth finger 21 f completes the opening operation, the amount oftransport of a liquid per cycle is less than a defined amount. Inaddition, variations occur in the state of restoration of the part ofthe tube 22 where the sixth finger 21 f abuts on, resulting invariations in the amount of transport of a liquid per cycle.

Therefore, in the liquid transport device 1 in the present embodiment,the control unit 110 controls the drive mechanism 111 in a manner inwhich the first finger 21 a on the most upstream side of the transportdirection starts the closing operation after the seventh finger 21 g onthe most downstream side of the transport direction completes theclosing operation, and the sixth finger 21 f that is second from thedownstream side of the transport direction completes the openingoperation. That is to say, “filled-up time” that is a period of time e-fobtained by subtracting the time f at which the sixth finger 21 gcompletes the opening operation from the time e at which the firstfinger 21 a starts the closing operation is set to be greater than zero.This can reduce variations and errors deviated from a defined amount inthe amount of transport of a liquid per cycle (the amount of a liquidillustrated by the hatched portion in FIG. 6), and a liquid can betransported with high accuracy.

Specifically, the period of time of restoration of the tube 22, that is,the period of time from the start of the opening operation until thecompletion thereof (for example, from the time c to the time d) may bedetermined in advance, and the speed of rotation of the cam 104 may beadjusted in a manner of satisfying a condition of filled-up time>0. Forexample, in a case of using a tube 22 having weak resilience, theinterval (period of time t) between the start time of the closingoperation by the fingers 21 is increased by decreasing the speed ofrotation of the cam 104. Then, the start of the closing operation by thefirst finger 21 a is delayed, and thus the sixth finger 21 f cancomplete the opening operation before the first finger 21 a starts theclosing operation.

Difference in Cross-Sectional Extent of Tube Depending on Temperature

FIG. 9 is a graph illustrating the amount of transport of a liquid whenthe ambient temperature of the tube 22 and the speed of rotation of thecam 104 are changed. Here, the amount of transport of a liquid isillustrated in weight according to the method of testing an infusionpump in the IEC standards. FIG. 9 is a graph that plots the amount of aliquid transported by one rotation of the cam 104 when the ambienttemperature of the tube 22 is changed to various values (at a pitch of5° C. from 5° C. to 40° C.), and the speed of rotation of the cam 104 ischanged to various values (1500, 3000, 4500, and 9000 (μl/h)) in theliquid transport device 1 in the present embodiment. The horizontal axisindicates a temperature (° C.), and the vertical axis indicates anamount of transport of a liquid (g). The unit of the speed of rotationof the cam 104 is “μl/h”. This unit represents the speed at which thecam 104 is rotated in a manner in which a predetermined amount of aliquid (μl) is transported per hour (h). In addition, FIG. 9 is a resultof measurement in a state where the above condition of “filled-uptime>0” is satisfied.

In the graph in FIG. 9, when the ambient temperature of the tube 22 isnot changed, the amount of transport of a liquid per rotation of the cam104 is substantially constant even when the speed of rotation of the cam104 is changed. It is understood from the result that a constant amountof a liquid can be transported even when the speed of rotation of thecam 104 is changed provided that the condition of “filled-up time>0” issatisfied.

Meanwhile, in the graph in FIG. 9, the amount of transport of a liquidis small in the area where the ambient temperature of the tube 22 islow. That is to say, it is understood that errors occur in the amount oftransport of a liquid due to a difference in the ambient temperature ofthe tube 22 even though the condition of “filled-up time>0” issatisfied. This is considered, as will be described below, to be causedby characteristics of the material (for example, a resin material suchas a styrene-based thermoplastic elastomer and an olefin-basedthermoplastic elastomer), which constitutes the tube 22, changingdepending on temperature.

FIG. 10 is a diagram representing a difference in the cross-sectionalextent of the tube 22 due to a difference in the ambient temperature ofthe tube 22. FIG. 10 is a cross-sectional view that is taken by cuttingthe tube 22 in a direction which is perpendicular to the axial direction(transport direction) of the tube 22. In addition, FIG. 10 is a diagramthat represents a state where the opening operation for the tube 22 iscompleted, that is, a state where the tube 22 is restored with theelasticity thereof from a state where the tube 22 is squeezed by thefingers 21. As illustrated in the left drawing in FIG. 10, when theambient temperature of the tube 22 is Ta, and the rubberiness (Young'smodulus) of the resin material constituting the tube 22 is high, an arcpart of the tube 22 tends to extend, and the cross-sectional shape ofthe tube 22 becomes a shape close to a circle. Meanwhile, as illustratedin the right drawing in FIG. 10, when the ambient temperature of thetube 22 is Tb that is different from Ta, and the rubberiness of the tube22 is low, a force that extends the arc part of the tube 22 is small,and the cross-sectional shape of the tube 22 becomes an elliptic shape.

As such, when the ambient temperature of the tube 22 changes, thecross-sectional shape of the tube 22 is changed, and the cross-sectionalextent (Aa and Ab) of the inside of the tube 22 is changed even in astate where the opening operation for the tube 22 is completed. That isto say, the internal volume of the tube 22 is changed. Thus, even thoughthe condition of “filled-up time>0” is satisfied, the amount of a liquidcaptured in the part of the tube 22 where the first to the sixth fingers21 a to 21 f abut on (the amount of a liquid illustrated by the hatchedportion in FIG. 6) slightly varies depending on the ambient temperatureof the tube 22 when the first finger 21 a starts the closing operation,and errors occur in the amount of transport of a liquid per cycle.

In the liquid transport device 1 in the present embodiment, the controlunit 110 controls the rate of driving of the drive mechanism 111, thatis, the amount of rotation (angle of rotation) of the cam 104 in thepresent embodiment in a corrective manner on the basis of the ambienttemperature of the tube 22. In doing so, errors in the amount oftransport of a liquid due to a difference in the ambient temperature ofthe tube 22, that is, a difference in the internal volume of the tube 22are supplemented, and a defined amount of a liquid is transported withhigh accuracy regardless of the ambient temperature of the tube 22. Therate of driving of the drive mechanism 111 that is corrected on thebasis of the ambient temperature of the tube 22 is not limited to theamount of rotation of the cam 104. For example, the rate of driving ofthe drive mechanism 111 may be the amount of rotation of the rotor wheel105 or the rate of driving of the piezoelectric motor 100 (the number oflongitudinal vibrations or flexural vibrations).

Control of Amount of Rotation of Cam 104

FIG. 11 illustrates a correction table for the amount of rotation of thecam 104. FIG. 12 illustrates the flow of a liquid transport method inthe liquid transport device 1. In the present embodiment,exemplification is provided for a case where the drive mechanism 111 isdriven intermittently, not being driven continuously. That is to say,the control unit 110 controls the drive mechanism 111 in a manner inwhich a transport operation of transporting a liquid in the tube 22 withdrive of the plurality of fingers 21 and a stopping operation of nottransporting a liquid in the tube 22 with stopping of drive of theplurality of fingers 21 are repeated alternately.

The memory 110 b that the control unit 110 includes stores thecorrection table illustrated in FIG. 11. In the correction table,“ambient temperature of the tube 22” is associated with “correctioncoefficient of the amount of rotation of the cam 104”. In addition, avalue obtained by multiplying the reference amount of rotation of thecam 104 (for example, 1000 rotations) by the correction coefficient is acorrected amount of rotation. Here, exemplification is provided for acase where the amount of transport of a liquid when the ambienttemperature of the tube 22 is 20° C. is set as a reference amount, theamount of transport of a liquid is less than the reference amount whenthe ambient temperature of the tube 22 is lower than 20° C., and theamount of transport of a liquid is greater than the reference amountwhen the ambient temperature of the tube 22 is higher than 20° C. Thus,in the correction table in FIG. 11, the correction coefficient thatcorresponds to the ambient temperature of the tube 22 of 20° C. is setto one, the correction coefficient that corresponds to the ambienttemperature which is lower than 20° C. is set to be greater than one,and the correction coefficient that corresponds to the ambienttemperature which is higher than 20 degrees is set to be less than one.

Not only the correction coefficient but also “corrected amount ofrotation” may be associated with “ambient temperature of the tube 22”when the amount of a liquid that is transported in one transportoperation is fixed. This can facilitate control by the control unit 110because the control unit 110 does not need to compute the correctedamount of rotation by multiplying the reference amount of rotation bythe correction coefficient at each time of association.

A characteristic of change in the amount of transport of a liquid withrespect to the ambient temperature of the tube 22 changes when thematerial and the like that constitute the tube 22 are changed. Thus,although the amount of transport of a liquid is decreased in the areawhere the ambient temperature of the tube 22 is low in FIG. 9, inaddition to this, for example, the amount of transport of a liquid maybe decreased in the area where the ambient temperature of the tube 22 ishigh. The correction table needs to be changed when the tube 22 ischanged. Therefore, as illustrated in the graph in FIG. 9, the amount ofa liquid that the liquid transport device 1 transports may be actuallymeasured when the ambient temperature of the tube 22 is changedvariously, and the correction table for the amount of rotation of thecam 104 may be created on the basis of the result of measurement.

As illustrated in FIG. 12, the control unit 110 first obtains theambient temperature of the tube 22 when the transport operation isstarted on the basis of an instruction from a user or at a set timing(S01). The temperature sensor 109 (refer to FIG. 2) that is used incontrol of drive of the piezoelectric motor 100, that is, thetemperature sensor 109 that measures the ambient temperature of thepiezoelectric motor 100 is set as a temperature sensor that measures theambient temperature of the tube 22 in the present embodiment.

This can reduce the number of components when compared with a case ofdisposing a dedicated temperature sensor that measures the ambienttemperature of the tube 22 and thus can reduce cost. Besides thetemperature sensor 109, for example, a dedicated temperature sensor thatmeasures the ambient temperature of the tube 22 may be disposed incontact with the tube 22. This can obtain the ambient temperature of thetube 22 with higher accuracy.

Next, the control unit 110 obtains the corrected amount of rotation ofthe cam 104 in one transport operation on the basis of the ambienttemperature of the tube 22 that is obtained from the temperature sensor109 and the correction table (FIG. 11) that is stored on the memory 110b (S02). When the ambient temperature of the tube 22 is different fromthe temperature that is set in the correction table (for example, 22°C.), the control unit 110 obtains the corrected amount of rotation byinterpolating a corrected amount of rotation between the correctedamounts of rotation that correspond to the previous and the nexttemperatures (for example, 20° C. and 25° C.)

Next, the control unit 110 drives the piezoelectric motor 100 in amanner in which the cam 104 rotates by the corrected amount of rotationand drives the plurality of fingers 21 (S03). At this time, the controlunit 110 rotates the cam 104 at a speed of rotation that satisfies thecondition of filled-up time>0 and controls the speed of rotation of thecam 104 at a constant rate regardless of the ambient temperature of thetube 22. After the cam 104 rotates by the corrected amount of rotation,the control unit 110 stops driving the piezoelectric motor 100 (S04) andtransitions from the transport operation to the stopping operation. Thecontrol unit 110 drives the piezoelectric motor 100 on the basis ofinformation that is obtained from the rotary encoder which measures theamount of rotation (angle of rotation) of the cam 104 until the cam 104rotates by the corrected amount of rotation.

As such, in the liquid transport device 1 in the present embodiment, thecontrol unit 110 controls the drive mechanism 111 in a manner in whichthe first finger 21 a on the most upstream side of the transportdirection starts the closing operation after the seventh finger 21 g onthe most downstream side of the transport direction completes theclosing operation, and the sixth finger 21 f that is second from thedownstream side of the transport direction completes the openingoperation. This can reduce variations and errors deviated from a definedamount in the amount of transport of a liquid per cycle.

The control unit 110 further controls the amount of rotation of the cam104 in a corrective manner on the basis of the result of measurement bythe temperature sensor 109 that measures the ambient temperature of thetube 22. Thus, even when the cross-sectional extent of the inside of thetube 22 after the opening operation is completed is changed depending onthe ambient temperature of the tube 22, errors in the amount oftransport of a liquid due to a difference in the ambient temperature(internal volume) of the tube 22 can be supplemented by correcting theamount of rotation of the cam 104. Therefore, the liquid transportdevice 1 in the present embodiment can transport a liquid with highaccuracy regardless of the ambient temperature of the tube 22, and forexample, a liquid medicine and the like can be precisely injected into aliving body.

The amount of transport of a liquid per rotation of the cam 104 issubstantially constant even when the speed of rotation of the cam 104 ischanged provided that the condition of filled-up time>0 is satisfied,and the ambient temperature of the tube 22 is not changed (FIG. 9). Thatis to say, since errors deviated from a defined amount of transport of aliquid when the cam 104 rotates by a defined amount of rotation (forexample, 1000 rotations) do not change independently of the speed ofrotation of the cam 104, the correction coefficient that supplements theerrors does not need to be obtained by associating the correctioncoefficient with the speed of rotation of the cam 104. When thecondition of filled-up time>0 is not considered, the state ofrestoration of the sixth finger 21 f that is second from the downstreamside varies depending on the speed of rotation of the cam 104 inaddition to the internal volume of the tube 22 changing depending on theambient temperature of the tube 22. Thus, the correction coefficientneeds to be associated with not only the ambient temperature of the tube22 but also the speed of rotation of the cam 104. Therefore, accordingto the liquid transport device 1 in the present embodiment, the numberof correction coefficients that correct the amount of rotation of thecam 104 can be decreased, the capacity of the memory 110 b of thecontrol unit 110 can be decreased, and control by the control unit 110can be facilitated.

The assumption is made here that the speed of rotation of the cam 104,not the amount of rotation of the cam 104, is corrected on the basis ofthe ambient temperature (internal volume) of the tube 22. When, forexample, the internal volume of the tube 22 is small, errors in theamount of transport of a liquid can be supplemented by rotating the cam104 at a faster speed than a reference speed and increasing the amountof rotation of the cam 104 in a predetermined period of time. In thiscase, however, when errors occur in the speed of rotation of the cam104, the cam 104 cannot be rotated by an amount of rotation that cansupplement errors in the amount of transport of a liquid. As a measureagainst this, the liquid transport device 1 in the present embodimentcorrects the amount of rotation of the cam 104 on the basis of theambient temperature of the tube 22. Thus, errors hardly occur in theamount of rotation of the cam 104 when compared with a case ofcorrecting the speed of rotation of the cam 104, and the cam 104 can berotated more securely by an amount of rotation that can supplementerrors in the amount of transport of a liquid. Therefore, the liquidtransport device 1 in the present embodiment can transport a liquid withhigher accuracy.

In addition, the transport operation of a liquid and the stoppingoperation are alternately repeated in the liquid transport device 1 inthe present embodiment. Thus, an increase or a decrease in theprocessing time of the transport operation does not pose a problembecause the amount of rotation of the cam 104 is corrected on the basisof the ambient temperature of the tube 22. Therefore, the extent offreedom is high in setting the speed of rotation of the cam 104 evenwhen the amount of rotation of the cam 104 is corrected, and the speedof rotation of the cam 104 can be constant regardless of the ambienttemperature of the tube 22 as in the present embodiment. As such, makingthe speed of rotation of the cam 104 constant can facilitate control bythe control unit 110. The condition of filled-up time>0 is alsosatisfied easily when the extent of freedom is high in setting the speedof rotation of the cam 104.

The speed of rotation of the cam 104 is not limited to a constant value.The control unit 110 may change the speed of rotation of the cam 104 toan extent that satisfies the condition of filled-up time>0. This canadjust the processing time of the transport operation to a desiredprocessing time such as a constant processing time and a shortenedprocessing time regardless of the ambient temperature of the tube 22 byadjusting the speed of rotation of the cam 104 depending on thecorrected amount of rotation of the cam 104 while allowing the liquidtransport device 1 to transport a liquid with high accuracy. There maybe a case, such as a case of controlling a phase difference, where thespeed of rotation of the motor (and the cam connected to the motor) isnot determined depending on a method of controlling the motor. Even insuch a case, a liquid may be transported by driving the motor to anextent in which the speed of rotation of the motor satisfies thecondition of filled-up time>0 so that the cam 104 rotates by thecorrected amount of rotation. This can transport a liquid with highaccuracy.

There are injection methods available when the liquid transport device 1is used as, for example, an insulin injecting device. One is aninjection method (bolus) of increasing the amount of injection ofinsulin along with a temporary rise in blood sugar when a user takes infood. Another one is a method (basal) of injecting a constant amount ofinsulin continuously in a normal case. The transport operation and thestopping operation are alternately repeated according to such variousinjection methods. When, for example, the interval between the transportoperations is long, the amount of rotation of the cam 104 may becorrected by obtaining the ambient temperature of the tube 22 prior tothe start of the transport operation as illustrated in the flow in FIG.12. Meanwhile, when the interval between the transport operations isshort, the amount of rotation of the cam 104 does not have to benecessarily corrected for each transport operation. The amount ofrotation of the cam 104 may be corrected by obtaining the ambienttemperature of the tube 22 for every predetermined time (for example,for every 30 minutes) or for every predetermined numbers of thetransport operation.

Not limited to being driven intermittently, the liquid transport device1 may transport a liquid in a manner in which the cam 104 rotates at alltimes. In this case, the amount of rotation of the cam 104 per unit timeis corrected depending on the ambient temperature of the tube 22. Thus,the control unit 110 changes the speed of rotation of the cam 104 to anextent that satisfies the condition of filled-up time>0. The controlunit 110 may correct the amount of rotation of the cam 104 per unit timeby obtaining the ambient temperature of the tube 22 for everypredetermined time (for example, for every 30 minutes).

OTHER EMBODIMENTS

The above embodiment is intended to facilitate understanding of theinvention, not intended to interpret the invention in a limited manner.It is needless to say that modifications and improvements may be carriedout to the invention without departing from the gist of the invention,and the equivalents of the modifications and the improvements areincluded in the invention.

In the above embodiment, exemplification is provided for the rotaryliquid transport device 1 in which the plurality of fingers 21 isarranged between the arc-shaped tube 22 and the cam 104 radially fromthe center of rotation of the cam 104. However, the invention is notlimited to this. For example, a direct-drive liquid transport device inwhich a plurality of fingers is arranged along a tube that extends in alinear direction may be used. Even in this case, a drive mechanism ofthe fingers is controlled in a manner in which the condition offilled-up time>0 is satisfied. The drive mechanism is controlled in amanner in which the fingers 21 are operated for a number of cycles inwhich errors in the amount of transport of a liquid due to a differencein the ambient temperature of the tube can be supplemented or areoperated until reaching positions in the linear direction. This cantransport a liquid with high accuracy.

In the above embodiment, the liquid transport device 1 is provided withthe catheter 310 and the like because exemplification is provided for acase where the liquid transport device 1 is used to inject a liquid intoa living body. However, the invention is not limited to this. Theinvention is desirably and effectively applied to a peristaltic liquidtransport device that is provided with a tube, a plurality of fingers,and a drive mechanism which drives the fingers.

The entire disclosure of Japanese Patent Application No. 2014-98372,filed May 12, 2014 is expressly incorporated by reference herein.

What is claimed is:
 1. A liquid transport device comprising: a tube thathas elasticity and is intended to transport a liquid in a transportdirection; a plurality of fingers that is lined up along the transportdirection; a drive mechanism that drives the plurality of fingers; atemperature sensor that measures the ambient temperature of the tube;and a control unit that controls the drive mechanism in a manner inwhich a liquid inside the tube is transported in the transport directionby repeating a closing operation of squeezing the tube with the fingerand an opening operation in which the finger is pressed back by theshape of the squeezed tube being restored, wherein the control unitcontrols the drive mechanism in a manner in which the finger on the mostupstream side of the transport direction starts the closing operationafter the finger on the most downstream side of the transport directioncompletes the closing operation, and the finger that is second from thedownstream side of the transport direction completes the openingoperation, and controls the rate of driving of the drive mechanism in acorrective manner on the basis of a result of measurement by thetemperature sensor.
 2. The liquid transport device according to claim 1,wherein the rate of driving of the drive mechanism is the amount ofrotation of the drive mechanism.
 3. The liquid transport deviceaccording to claim 1, wherein the drive mechanism includes apiezoelectric motor, and the temperature sensor is a sensor thatmeasures the ambient temperature of the piezoelectric motor for use incontrol of drive of the piezoelectric motor.
 4. The liquid transportdevice according to claim 1, wherein the control unit controls the drivemechanism in a manner in which the speed of drive of the drive mechanismis constant.
 5. The liquid transport device according to claim 1,wherein the control unit changes the speed of the drive mechanism to anextent in which the finger on the most upstream side starts the closingoperation after the finger on the most downstream side completes theclosing operation, and the finger that is second from the downstreamside completes the opening operation.
 6. The liquid transport deviceaccording to claim 1, wherein the extent of the cross section of theinside of the tube after the opening operation is completed, the crosssection being taken by cutting the tube in a direction that isperpendicular to the axial direction of the tube, changes depending onthe ambient temperature of the tube.
 7. The liquid transport deviceaccording to claim 1, wherein the control unit controls the drivemechanism in a manner in which a transport operation of transporting aliquid in the tube with drive of the plurality of fingers and a stoppingoperation of not transporting a liquid in the tube with stopping ofdrive of the plurality of fingers are alternately repeated.
 8. A liquidtransport method for a liquid transport device that includes a tubewhich has elasticity and is intended to transport a liquid in atransport direction, a plurality of fingers which is lined up along thetransport direction, and a drive mechanism which drives the plurality offingers, in which a liquid in the tube is transported in the transportdirection by repeating a closing operation of squeezing the tube withthe finger and an opening operation in which the finger is pressed backby the shape of the squeezed tube being restored, the method comprising:obtaining the ambient temperature of the tube; and driving the pluralityof fingers with the drive mechanism at a rate of driving that iscorrected on the basis of the ambient temperature and driving theplurality of fingers in a manner in which the finger on the mostupstream side of the transport direction starts the closing operationafter the finger on the most downstream side of the transport directioncompletes the closing operation, and the finger that is second from thedownstream side of the transport direction completes the openingoperation.